Measurement of the inclusive electron spectrum in charmless semileptonic B decays near the kinematic endpoint and determination of |V(ub)|.

We present a measurement of the inclusive electron spectrum in B→Xueν decays near the kinematic limit for B→Xceν transitions, using a sample of 88×10^6 BB̅ pairs recorded by the BABAR detector at the Υ(4S) resonance. Partial branching fraction measurements are performed in five overlapping intervals of the electron momentum; for the interval of 2.0–2.6   GeV/c we obtain ΔB(B→Xueν)=(0.572±0.041stat±0.065syst)×10-3. Combining this result with shape function parameters extracted from BABAR measurements of moments of the inclusive photon spectrum in B→Xsγ decays and moments of the hadron-mass and lepton-energy spectra in B→Xcℓν decays we determine |Vub|=(4.44±0.25exp-0.38SF+0.42±0.22theory)×10-3. Here the first error represents the combined statistical and systematic experimental uncertainties of the partial branching fraction measurement, the second error refers to the uncertainty of the determination of the shape function parameters, and the third error is due to theoretical uncertainties in the QCD calculations.